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This chapter is from the book

Using the Lens Corrections tab

Via the Lens Corrections tab in Camera Raw, you can correct a photo for various adverse effects of lens distortion. You can straighten out an architectural feature, such as a building or fence, that looks as if it’s leaning toward or away from the viewer, or that is tilted horizontally (isn’t level); and you can correct for under- or overexposure at the edges of a photo (vignetting). The corrections can be applied using a preset profile (this page) or manually (pages 79–81).

To correct geometric distortion and vignetting via Profile settings: star.jpg

  1. Click the Lens Corrections tab. c0078-01.jpg Double-click the Hand tool c0057-02.jpg to fit the image in the preview.
  2. To access predefined lens profiles, click the Profile tab, then check Enable Lens Profile Corrections.
  3. From the Setup menu, A do the following:
    f0078-01.jpg

    A Check Enable Lens Profile Corrections, then choose Auto from the Setup menu …

    Choose Auto to have Camera Raw read the EXIF metadata in the photo and attempt to select the proper lens make, model, and predefined profile.

    If an error message indicates that the Auto option was unable to locate a profile, choose your lens manufacturer from the Make menu. B Camera Raw will locate a matching lens model and list it on the

    f0078-02.jpg

    B … or choose your lens maker from the Make menu. Regardless of the Setup option, if necessary, adjust the Distortion value.

    Model menu, and will locate a predefined profile and list it on the Profile menu. If the Model menu lists more than one model, choose the one with which the photo was shot.

  4. Under Correction Amount, do the following:

    Set the Distortion value to control the amount of correction.

    Set the Vignetting value to correct for under- or overexposure at the edges of the photo.

  5. Optional: If Camera Raw managed to locate your lens profile (step 3), you can save that profile and any custom Correction Amount settings as your new default profile by choosing Save New Lens Profile Defaults from the Setup menu. In future Camera Raw editing sessions, if you choose Default from the Setup menu, and the current photo was taken with this lens, the saved profile and settings will be applied. (To restore the Adobe predefined settings for your chosen lens, from the Setup menu, choose Reset Lens Profile Defaults.)
  6. Optional: If you want to further correct any lens distortion manually, see the next task.

To correct geometric distortion or vignetting via the Manual tab: star.jpg

  1. Click the Lens Corrections tab, c0078-01.jpg and double-click the Hand tool c0057-02.jpg to fit the image in the preview. A
    f0079-01.jpg

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    A The original photo (above) shows signs of lens distortion: The house looks as if it’s tilting away from the camera, and it’s not level.

  2. Click the Manual tab. B
    f0079-02.jpg

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    B We clicked the Manual tab (under Lens Corrections) to access these menu options and sliders.

  3. In the Upright area, click a button to apply a preset correction:

    Auto c0079-01.jpg to apply level correction and fix horizontal and vertical convergence, balanced with as little distortion as possible. C

    f0079-03.jpg

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    C Under Upright, we clicked the Auto button for a balanced correction. This partially corrected the vertical lines and vertical tilt, but the left side of the house still looks as if it’s farther away from the viewer than the right side.

    Level c0079-02.jpg to apply only level correction (not fix horizontal or vertical convergence).

    Vertical c0079-03.jpg to apply level correction and fix vertical convergence (but not horizontal convergence).

    Full c0079-04.jpg for a stronger correction of horizontal and vertical convergence, in addition to level correction (A, next page).

    f0080-01.jpg

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    A We clicked the Full button instead, which successfully made the house level and upright. To lighten the outer areas of the photo, we increased the Amount value (under Lens Vignetting).

  4. If further manual correction is needed, do any of the following:

    To spread the image out (fix pincushion distortion), lower the Distortion value; or to pinch the image inward (fix barrel distortion), increase the Distortion value.

    • To display a grid over the image so you can check the alignment, check Show Grid or press V. Adjust the grid size via the slider. B
    f0080-03.jpg

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    B We made some minor Vertical and Rotate adjustments, with Show Grid checked to help us gauge the effect.

    f0080-02.jpg

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    To widen the top of the image, (correct key-stoning) reduce the Vertical value; to widen the bottom of the image, increase the Vertical value. Readjust the Distortion value, if needed.

    To widen the left edge of the image, reduce the Horizontal value; to widen the right edge of the image, increase the Horizontal value.

    To rotate the image, change the Rotate value.

    To enlarge or shrink the photo, change the Scale value. Note: You could crop the photo instead.

    To stretch the image horizontally or vertically, change the Aspect value. This option is useful for correcting strong perspective distortion in photos taken with a wide-angle lens (A–B, next page).

    f0081-01.jpg

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    A We tried increasing the Aspect value, but this setting exaggerated and distorted the verticals of the house too much.

    f0081-02.jpg

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    B Instead, we set the Aspect value to –5, which exaggerated the horizontal proportion only slightly. The final settings we chose for the image are shown at right.

    • If you moved the Distortion slider, you can click Reanalyze (below the buttons) to force a recalculation of the Upright correction based on the Distortion value. If you want to turn off (but preserve) all your Upright corrections, click the Off button. c0080-01.jpg If you click a different Upright button, as an alert will inform you, all the Transform sliders (except Distortion) will be reset to 0.
  5. To correct or apply Lens Vignetting (lighten or darken the outer areas of the photo), set the Amount value for the strength of the correction, then set the Midpoint value to expand the vignette inward or outward. Readjust the Amount value, if needed.

    • To learn about the Lens Correction filter in Photoshop, see pages 332–333 and 439.

Another use for the Lens Corrections tab is to correct for chromatic aberration (blue-yellow or red-green color shifts), as well as purple or green color fringes. These occur when a camera lens (especially one that is set to a wide aperture) doesn’t properly focus all the wavelengths of colored light precisely to the same spot.

To correct color shifts and/or fringes: star.jpg

  1. Click the Lens Corrections tab, c0082-01.jpg then click the Color tab.
  2. To remove any blue-yellow or red-green color shifts, check Remove Chromatic Aberration.A–B
    f0082-01.jpg

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    A We noticed a purple fringe along the edge of the stone semicircle in this photo.

    f0082-02.jpg

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    B To remove any blue-yellow and red-green color shifts, we checked Remove Chromatic Aberration.

  3. Zoom to 100% view on an area where you suspect there is a purple or green color fringe, and with the Hand tool (H), center it in the preview.

    Adjust the Purple Amount and/or Green Amount values. The higher the value, the wider the area on the edges of shapes in which fringe removal occurs. If the photo contains objects that are purple or green, beware of setting too high a correction value, which could degrade their color.

    • To help you locate which areas of a photo contain purple or green fringes, zoom out, then Alt/Option click-and-hold on the Purple Amount or Green Amount slider. Areas where the fringe is present display as black. C–D Purple fringes commonly occur around specular highlights. Zoom back in when you're done.
    f0082-03.jpg

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    C To preview any purple fringe as black, with Alt/Option held down, we clicked and held the Purple Amount slider. Black displayed along the edge of the stone semicircle.

    f0082-04.jpg

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    D To preview any green fringe as black, with Alt/ Option held down, we clicked and held the Green Amount slider. No black displayed, a sign that green fringe wasn’t an issue in this area of the photo.

To control the range of hues that the Purple Amount and Green Amount sliders affect (in other words, the area in which fringe removal occurs), drag the Purple Hue or Green Hue bar over a hue area on the spectrum (the spectrum of affected colors displays within the bar) and/or widen or narrow the range by dragging either endpoint of the bar. (To reset the bar to its default length and position, double-click within it.)

  • To display the affected colors temporarily as black in the preview, zoom out a bit, then with Alt/Option held down, drag the Purple Hue or Green Hue bar. A–D
f0083-01.jpg

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A We increased the Purple Amount value, then held down Alt/Option and dragged the Purple Hue bar slightly to the left. At this setting, the fringe correction was affecting the top of the stone semicircle — which wasn’t our intention.

f0083-02.jpg

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B We held down Alt/Option and dragged the Purple Hue bar to the right, then dragged the right endpoint inward to narrow the range. At this setting, the fringe correction is affecting primarily the edge of the semicircle — mission accomplished.

f0083-03.jpg

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C Compare this original image to the final image, which is shown at right.

f0083-04.jpg

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D The purple fringe is gone from the edge of the semicircle.

  • When adjusting a photo that contains foliage, avoid positioning the Green Hue bar over the orange/yellow color range (at the left end of the spectrum), which could gray out the essential yellows in the image.
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